Probe card assembly

ABSTRACT

In a probe card assembly, a series of probe elements can be arrayed on a silicon space transformer. The silicon space transformer can be fabricated with an array of primary contacts in a very tight pitch, comparable to the pitch of a semiconductor device. One preferred primary contact is a resilient spring contact. Conductive elements in the space transformer are routed to second contacts at a more relaxed pitch. In one preferred embodiment, the second contacts are suitable for directly attaching a ribbon cable, which in turn can be connected to provide selective connection to each primary contact. The silicon space transformer is mounted in a fixture that provides for resilient connection to a wafer or device to be tested. This fixture can be adjusted to planarize the primary contacts with the plane of a support probe card board.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This patent application is a continuation-in-part ofcommonly-owned, U.S. Provisional Patent Application No. 60/040,983 filedMar. 17, 1997 by Khandros and Sporck (status: pending)

[0002] which is a continuation-in-part of commonly-Owned, U.S. patentapplication Ser. No. 08/554,902 filed Nov. 9, 1995 by Eldridge, Grube,Khandros and Mathieu (status: pending), and its counterpart PCT patentapplication number PCT/US95/14844 filed Nov. 13, 1995 (published asWO96/15458),

[0003] which are continuations-in-part of commonly-owned, U.S. patentapplication Ser. No. 08/452,255 (hereinafter “PARENT CASE”), filed May26, 1995 by Eldridge, Grube, Khandros and Mathieu (status: pending), andits counterpart PCT patent application number PCT/US95/14909 filed Nov.13, 1995 (published as WO96/17378),

[0004] which are continuations-in-part of commonly-owned, U.S. patentapplication Ser. No. 08/340,144 filed Nov. 15, 1994 by Khandros andMathieu (status: pending) and its counterpart PCT patent applicationnumber PCT/US94/13373 filed Nov. 16, 1994 (published as WO95/14314),which are continuations-in-part of commonly-owned, copending U.S. patentapplication Ser. No. 08/152,812, filed Nov. 16, 1993 by Khandros(status: issued as U.S. Pat. No. 5,476,211).

TECHNICAL FIELD OF THE INVENTION

[0005] The invention relates to an apparatus and associated techniquesfor making pressure connections between electronic components withresilient (spring) contact elements, such as for performing test andburn-in procedures on semiconductor devices prior to their packaging,preferably prior to the individual semiconductor devices beingsingulated from a semiconductor wafer.

BACKGROUND OF THE INVENTION

[0006] The aforementioned commonly-owned, copending U.S. patentapplication Ser. No. 08/554,902 filed Nov. 9, 1995 and its correspondingPCT Patent Application No. PCT/US95/14844 filed Nov. 13, 1995(WO96/15458, published May 23, 1996), both by ELDRIDGE, GRUBE, KHANDROSand MATHIEU, disclose a probe card assembly. As illustrated, forexample, in FIG. 5 therein, the probe card assembly (500) includes aprobe card (502), a space transformer (506) having resilient contactstructures (probe elements 524) mounted directly to and extending fromterminals (522) on a surface thereof, and an interposer (504) disposedbetween the space transformer (506) and the probe card (502). The spacetransformer (506) and interposer (504) are “stacked up” so that theorientation of the space transformer (506), hence the orientation of thetips of the probe elements (524), can be adjusted without changing theorientation of the probe card. Suitable mechanisms (532, 536, 538, 546)for adjusting the orientation of the space transformer (506), and fordetermining what adjustments to make, are disclosed therein. Multipledie sites on a semiconductor wafer (508) are readily probed using thedisclosed techniques, and the probe elements (524) can be arranged tooptimize probing of an entire wafer (508). As shown, for example, inFIG. 2A therein, the resilient contact structures or probe elements(524) are suitably (but not limited to) composite interconnectionselements (200) having a relatively soft core (206) overcoated by arelatively hard shell (218, 220).

[0007] Generally, the present invention obviates the need for using aspace transformer (e.g., 506) and an interposer (504) in a probe cardassembly that may be adjusted in a manner similar to that described inthe above-referenced patent applications.

[0008] Among the problems associated with using a space transformercomponent in a probe card assembly is that of matching the coefficientsof thermal expansion of the space transformer to that of the wafer undertest (WUT). Furthermore, in some instances, depending on the materials(e.g., ceramic layers, terminals, etc.) and processes employed in themanufacture of the space transformer component, it can be difficult toachieve a reliable mechanical connection between free-standing resilient(spring) contact elements mounted to the terminals of the spacetransformer under the stresses encountered when making repeated pressureconnections to terminals of other electronic components, such as wouldbe encountered when probing a sequence of WUTs or a series of die siteson a one or more WUTs.

[0009] The use of a separate interposer component in a probe cardassembly can also be undesirable. Simply stated, it is one morecomponent that must successfully be yielded and incorporated into theprobe card assembly.

[0010] The present invention advantageously employs, but does notrequire applicant's own free-standing, resilient, “composite”interconnection elements, which are described in one or more of theabove referenced commonly-owned patents and patent applications.

[0011] Commonly-owned U.S. patent application Ser. No. 08/152,812 filedNov. 16, 1993 (now U.S. Pat. No. 4,576,211), and its counterpartcommonly-owned copending “divisional” U.S. patent application Ser. No.08/457,479 filed Jun. 1, 1995 (status: pending) and Ser. No. 08/570,230filed Dec. 11, 1995 (status: pending), all by KHANDROS, disclose methodsfor making resilient (spring) interconnection elements formicroelectronics applications involving mounting an end of a flexibleelongate core element (e.g., wire “stem” or “skeleton”) to a terminal onan electronic component coating the flexible core element and adjacentsurface of the terminal with a “shell” of one or more materials having apredetermined combination of thickness, yield strength and elasticmodulus to ensure predetermined force-to-deflection characteristics ofthe resulting spring contacts. Exemplary materials for the core elementinclude gold. Exemplary materials for the coating include nickel and itsalloys. The resulting spring contact element is suitably used to effectpressure, or demountable, connections between two or more electroniccomponents, including semiconductor devices, and is well-suited to useas a probe element of a probe card assembly.

[0012] Commonly-owned, copending U.S. patent application Ser. No.08/340,144 filed Nov. 15, 1994 and its corresponding PCT PatentApplication No. PCT/US94/13373 filed Nov. 16, 1994 (WO95/14314,published May 26, 1995), both by KHANDROS and MATHIEU, disclose a numberof applications for the aforementioned spring contact elements, and alsodiscloses techniques for fabricating contact pads at the ends of thespring contact elements. For example, in FIG. 14 thereof, a plurality ofnegative projections or holes, which may be in the form of invertedpyramids ending in apexes, are formed in the surface of a sacrificiallayer (substrate). These holes are then filled with a contact structurecomprising layers of material such as gold or rhodium and nickel. Aflexible elongate element is mounted to the resulting contact structureand can be overcoated in the manner described hereinabove. In a finalstep, the sacrificial substrate is removed. The resulting spring contacthas a contact pad having controlled geometry (e.g., sharp points) at itsfree end. Commonly-owned, copending U.S. patent application Ser. No.08/452,255 filed May 26, 1995 and its corresponding PCT PatentApplication No. PCT/US95/14909 filed Nov. 13, 1995 (WO96/17278,published Jun. 6, 1996), both by ELDRIDGE, GRUBE, KHANDROS and MATHIEU,disclose additional techniques and metallurgies for fabricating contacttip structures on sacrificial substrates, as well as techniques fortransferring a plurality of spring contact elements mounted thereto, enmasse, to terminals of an electronic component (see, e.g., FIGS. 11A-11Fand 12A-12C therein). These patent applications also disclose techniquesfor fabricating free-standing “composite” resilient (spring) contactelements directly on silicon substrates, including on active devices.

[0013] Commonly-owned, copending U.S. Provisional Patent Application No.60/005,189 filed May 17, 1996 and its corresponding PCT PatentApplication No. PCT/US96/08107 filed May 24, 1996 (WO96/37332, publishedNov. 28, 1996), both by ELDRIDGE, KHANDROS, and MATHIEU, disclosestechniques whereby a plurality of contact tip structures (see, e.g, #620in FIG. 6B therein) are joined to a corresponding plurality of elongatecontact elements (see, e.g., #632 of FIG. 6D therein) which are alreadymounted to an electronic component (#630). This patent application alsodiscloses, for example in FIGS. 7A-7E therein, techniques forfabricating “elongate” contact tip structures in the form ofcantilevers. The cantilever tip structures can be tapered, between oneend thereof and an opposite end thereof. The cantilever tip structuresof this patent application are suitable for mounting to already-existing(i.e., previously fabricated) raised interconnection elements (see,e.g., #730 in FIG. 7F) extending (e.g., freestanding) from correspondingterminals of an electronic component (see. e.g., #734 in FIG. 7F).

[0014] Commonly-owned, copending U.S. Provisional Patent Application No.60/024,555 filed Aug. 26, 1996, by ELDRIDGE, KHANDROS and MATHIEU,discloses, for example at FIGS. 2A-2C thereof, a technique whereby aplurality of elongate tip structures having different lengths than oneanother can be arranged so that their outer ends are disposed at agreater pitch than their inner ends. Their inner, “contact” ends may becollinear with one another, for effecting connections to electroniccomponents having terminals disposed along a line, such as a centerlineof the component.

[0015] The present invention addresses and is particularly well-suitedto making interconnections to modern microelectronic devices havingtheir terminals (bond pads) disposed at a fine-pitch. As used herein,the term “fine-pitch” refers to microelectronic devices that have theirterminals disposed at a spacing of less than 5 mils, such as 2.5 mils or65

m.

[0016] Individual semiconductor (integrated circuit) devices (dies) aretypically produced by creating several identical devices on asemiconductor wafer, using know techniques of photolithography,deposition, and the like. Generally, these processes are intended tocreate a plurality of fully-functional integrated circuit devices, priorto singulating (severing) the individual dies from the semiconductorwafer. In practice, however, certain physical defects in the waferitself and certain defects in the processing of the wafer inevitablylead to some of the dies being “good” (fully-functional) and some of thedies being “bad” (non-functional).

[0017] It is generally desirable to be able to identify which of theplurality of dies on a wafer are good dies prior to their packaging, andpreferably prior to their being singulated from the wafer. To this end,a wafer “tester” or “prober” may advantageously be employed to make aplurality of discrete pressure connections to a like plurality ofdiscrete connection pads (bond pads) on the dies. In this manner, thesemiconductor dies can be tested and exercised, prior to singulating thedies from the wafer.

[0018] A conventional component of a wafer tester is a “probe card” towhich a plurality of probe elements are connected tips of the probeelements effecting the pressure connections to the respective bond padsof the semiconductor dies.

[0019] Certain difficulties are inherent in any technique for probingsemiconductor dies. For example, modern integrated circuits include manythousands of transistor elements requiring many hundreds of bond padsdisposed in close proximity to one another (e.g., 5 milscenter-to-center). Moreover, the layout of the bond pads need not belimited to single rows of bond pads disposed close to the peripheraledges of the die (See, e.g., U.S. Pat. No. 5,453,583).

[0020] To effect reliable pressure connections between the probeelements and the semiconductor die one must be concerned with severalparameters including, but not limited to: alignment, probe force,overdrive, contact force, balanced contact force, scrub, contactresistance, and planarization. A general discussion of these parametersmay be found in U.S. Pat. No. 4,837,622, entitled HIGH DENSITY PROBECARD, incorporated by reference herein, which discloses a high densityepoxy ring probe card including a unitary printed circuit board having acentral opening adapted to receive a preformed epoxy ring array of probeelements.

[0021] Generally, prior art probe card assemblies include a plurality oftungsten needles extending as cantilevers from a surface of a probecard. The tungsten needles may be mounted in any suitable manner to theprobe card, such as by the intermediary of an epoxy ring, as discussedhereinabove. Generally, in any case, the needles are wired to terminalsof the probe card through the intermediary of a separate and distinctwire connecting the needles to the terminals of the probe card.

[0022] Probe cards are typically formed as circular rings, with hundredsof probe elements (needles) extending from an inner periphery of thering (and wired to terminals of the probe card). Circuit modules, andconductive traces (lines) of preferably equal length, are associatedwith each of the probe elements. This ring-shape layout makes itdifficult, and in some cases impossible, to probe a plurality ofunsingulated semiconductor dies (multiple sites) on a wafer, especiallywhen the bond pads of each semiconductor die are arranged in other thantwo linear arrays along two opposite edges of the semiconductor die.

[0023] Wafer testers may alternately employ a probe membrane having acentral contact bump area, as is discussed in U.S. Pat. No. 5,422,574,entitled LARGE SCALE PROTRUSION MEMBRANE FOR SEMICONDUCTOR DEVICES UNDERTEST WITH VERY HIGH PIN COUNTS, incorporated by reference herein. Asnoted in this patent, “A test system typically comprises a testcontroller for executing and controlling a series of test programs, awafer dispensing system for mechanically handling and positioning wafersin preparation for testing and a probe card for maintaining an accuratemechanical contact with the device-under-test (DUT).” (column 1, lines41-46).

[0024] Additional references, incorporated by reference herein, asindicative of the state of the art in testing semiconductor devices,include U.S. Pat. No. 5,442,282 (TESTING AND EXERCISING INDIVIDUALUNSINGULATED DIES ON A WAFER); U.S. Pat. No. 5,382,898 (HIGH DENSITYPROBE CARD FOR TESTING ELECTRICAL CIRCUITS); U.S. Pat. No. 5,378,982TEST PROBE FOR PANEL HAVING AN OVERLYING PROTECTIVE MEMBER ADJACENTPANEL CONTACTS); U.S. Pat. No. 5,339,027 (RIGID-FLEX CIRCUITS WITHRAISED FEATURES AS IC TEST PROBES); U.S. Pat. No. 5,180,977 (MEMBRANEPROBE CONTACT BUMP COMPLIANCY SYSTEM); U.S. Pat. No. 5,066,907 (PROBESYSTEM FOR DEVICE AND CIRCUIT TESTING); U.S. Pat. No. 4,757,256 (HIGHDENSITY PROBE CARD); U.S. Pat. No. 4,161,692 (PROBE DEVICE FORINTEGRATED CIRCUIT WAFERS); and U.S. Pat. No. 3,990,689 (ADJUSTABLEHOLDER ASSEMBLY FOR POSITIONING A VACUUM CHUCK).

[0025] Generally, interconnections between electronic components can beclassified into the two broad categories of “relatively permanent” and“readily demountable”.

[0026] An example of a “relatively permanent” connection is a solderjoint. Once two components are soldered to one another, a process ofunsoldering must be used to separate the components. A wire bond isanother example of a “relatively permanent” connection.

[0027] An example of a “readily demountable” connection is rigid pins ofone electronic component being received by resilient socket elements ofanother electronic component. The socket elements exert a contact force(pressure) on the pins in an amount sufficient to ensure a reliableelectrical connection therebetween.

[0028] Interconnection elements intended to make pressure contact withterminals of an electronic component are referred to herein as “springs”or “spring elements”. Generally, a certain minimum contact force isdesired to effect reliable pressure contact to electronic components(e.g., to terminals on electronic components). For example, a contact(load) force of approximately 15 grams (including as little as 2 gramsor less and as much as 150 grams or more, per contact) may be desired toensure that a reliable electrical connection is made to a terminal of anelectronic component which may be contaminated with films on itssurface, or which has corrosion or oxidation products on its surface.The minimum contact force required of each spring demands either thatthe yield strength of the spring material or that the size of the springelement are increased. As a general proposition, the higher the yieldstrength of a material, the more difficult it will be to work with(e.g., punch, bend, etc.). And the desire to make springs smalleressentially rules out making them larger in cross-section.

[0029] Probe elements are a class of spring elements of particularrelevance to the present invention. Prior art probe elements arecommonly fabricated from tungsten, a relatively hard (high yieldstrength) material. When it is desired to mount such relatively hardmaterials to terminals of an electronic component, relatively “hostile”(e.g., high temperature) processes such as brazing are required. Such“hostile” processes are generally not desirable (and often not feasible)in the context of certain relatively “fragile” electronic componentssuch as semiconductor devices. In contrast thereto, wire bonding is anexample of a relatively “friendly” processes which is much lesspotentially damaging to fragile electronic components than brazing.Soldering is another example of a relatively “friendly” process.However, both solder and gold are relatively soft (low yield strength)materials which will not function well as spring elements.

[0030] A subtle problem associated with interconnection elements,including spring contact elements, is that, often, the terminals of anelectronic component are not perfectly coplanar. Interconnectionelements lacking in some mechanism incorporated therewith foraccommodating these “tolerances” (gross non-planarities) will be hardpressed to make consistent contact pressure contact with the terminalsof the electronic component.

[0031] The following U.S. Patents, incorporated by reference herein, arecited as being of general interest vis-a-vis making connections,particularly pressure connections, to electronic components: U.S. Pat.Nos. 5,386,344 (FLEX CIRCUIT CARD ELASTOMERIC CABLE CONNECTOR ASSEMBLY);U.S. Pat. No. 5,336,380 (SPRING BIASED TAPERED CONTACT ELEMENTS FORELECTRICAL CONNECTORS AND INTEGRATED CIRCUIT PACKAGES); U.S. Pat. No.5,317,479 (PLATED COMPLIANT LEAD); U.S. Pat. No. 5,086,337 (CONNECTINGSTRUCTURE OF ELECTRONIC PART AND ELECTRONIC DEVICE USING THE STRUCTURE);U.S. Pat. No. 5,067,007 (SEMICONDUCTOR DEVICE HAVING LEADS FOR MOUNTINGTO A SURFACE OF A PRINTED CIRCUIT BOARD); U.S. Pat. No. 4,989,069(SEMICONDUCTOR PACKAGE HAVING LEADS THAT BREAK-AWAY FROM SUPPORTS); U.S.Pat. No. 4,893,172 (CONNECTING STRUCTURE FOR ELECTRONIC PART AND METHODOF MANUFACTURING THE SAME); U.S. Pat. No. 4,793,814 (ELECTRICAL CIRCUITBOARD INTERCONNECT); U.S. Pat. No. 4,777,564 (LEADFORM FOR USE WITHSURFACE MOUNTED COMPONENTS); U.S. Pat. No. 4,764,848 (SURFACE MOUNTEDARRAY STRAIN RELIEF DEVICE); U.S. Pat. No. 4,667,219 (SEMICONDUCTOR CHIPINTERFACE); U.S. Pat. No. 4,642,889 (COMPLIANT INTERCONNECTION ANDMETHOD THEREFOR); U.S. Pat. No. 4,330,165 (PRESS-CONTACT TYPEINTERCONNECTORS); U.S. Pat. No. 4,295,700 (INTERCONNECTORS); U.S. Pat.No. 4,067,104 (METHOD OF FABRICATING AN ARRAY OF FLEXIBLE METALLICINTERCONNECTS FOR COUPLING MICROELECTRONICS COMPONENTS); U.S. Pat. No.3,795,037 (ELECTRICAL CONNECTOR DEVICES); U.S. Pat. No. 3,616,532(MULTILAYER PRINTED CIRCUIT ELECTRICAL INTERCONNECTION DEVICE); and U.S.Pat. No. 3,509,270 (INTERCONNECTION FOR PRINTED CIRCUITS AND METHOD OFMAKING SAME).

BRIEF DESCRIPTION (SUMMARY) OF THE INVENTION

[0032] It is an object of the present invention to provide an improvedprobe card assembly.

[0033] It is an object of the present invention to provide a techniquefor probing semiconductor devices, particularly while they are residenton a semiconductor wafer.

[0034] It is another object of the present invention to provide atechnique for probing semiconductor devices that allows the tips of theprobe elements to be oriented without changing the position of the probecard.

[0035] According to the invention, a probe card assembly includes:

[0036] a probe card component such as a printed circuit board (PCB);

[0037] an interconnection substrate such as a silicon substrate or wafersupported above a surface of the probe card;

[0038] a plurality of resilient (spring) contact (probe) elementsmounted to and extending from a first plurality of terminals (e.g., bondpads) on the interconnection substrate;

[0039] means for making electrical connections to the probe elements viathe silicon substrate, such as a second plurality of terminals on thesilicon substrate which can be connected to with a flexible (ribbon)cable; and

[0040] means for adjusting the orientation of the interconnectionsubstrate relative to the probe card such as mounting plates anddifferential screws or electrical actuators.

[0041] Together, the interconnection substrate and probe elementscomprise a “probe card insert” which can be manufactured and sold as aunit for incorporation by others into a probe card assembly.

[0042] The probe card component, probe card insert, ribbon cable andmeans for adjusting the orientation of the interconnection substrate canbe manufactured and sold as a kit, for assembly by others into acomplete probe card assembly.

[0043] Generally, the silicon space transformer component permits aplurality of resilient contact structures extending from its top surfaceto make contact with terminals of an electronic component (i.e., bondpads on semiconductor devices) at a relatively fine pitch (spacing),while connections to the space transformer (i.e., to the bond pads or,alternatively, resilient contact structures) on its bottom surface areeffected at a relatively coarser pitch.

[0044] According to an aspect of the invention, the space transformerand interposer components of the probe card assembly may be provided asa “kit”, adapted for use with a probe card. Optionally, the mechanismfor adjusting the orientation of the space transformer can be includedin the “kit”.

[0045] According to an aspect of the invention, the resilient contactstructures (probe elements) extending from the top surface of thesilicon space transformer component may (or may not) be “compositeinterconnection elements” (defined hereinbelow).

[0046] According to an aspect of the invention, the resilient contactstructures extending from the top and bottom surfaces of the interposercomponent are “composite interconnection elements” (definedhereinbelow).

[0047] Other objects, features and advantages of the invention willbecome apparent in light of the following description thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Reference will be made in detail to preferred embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. The drawings are intended to be illustrative, not limiting.Although the invention will be described in the context of thesepreferred embodiments, it should be understood that it is not intendedto limit the spirit and scope of the invention to these particularembodiments.

[0049] Certain elements in selected ones of the drawings are illustratednot-to-scale, for illustrative clarity. Often, similar elementsthroughout the drawings are referred to by similar reference numerals.For example, the element 199 may be similar in many respects to theelement 299 in another figure. Also, often, similar elements arereferred to with similar numbers in a single drawing. For example, aplurality of elements 199 may be referred to as 199 a, 199 b, 199 c,etc.

[0050]FIG. 1 is an exploded view, partially in cross-section, of a probecard assembly such as is disclosed in the aforementioned U.S. patentapplication Ser. No. 08/554,902 and its counterpart PCT/US95/14844, andillustrates certain techniques which are relevant to the presentinvention.

[0051]FIG. 2 is a view, partially in cross-section, andpartially-schematic, of a probe card assembly similar to the probe cardassembly illustrated in FIG. 1 being aligned for use in testingsemiconductor wafers, such as is disclosed in the aforemetioned U.S.patent application Ser. No. 08/554,902 and its counterpartPCT/US95/14844, and illustrates certain techniques which are relevant tothe present invention.

[0052]FIG. 3 is a view, partially in cross-section, andpartially-schematic, of a technique for automatically adjusting theorientation of the space transformer component, such as is disclosed inthe aforemetioned U.S. patent application Ser. No. 08/554,902 and itscounterpart PCT/US95/14844, and illustrates certain techniques which arerelevant to the present invention.

[0053]FIG. 4 is a perspective view of a probe card insert, accoridng tothe invention.

[0054]FIG. 4A is a side schematic view of a probe card assemblyemploying the probe card insert of FIG. 4, according to the invention.

[0055]FIG. 4B is an exploded side view, partially in cross-section, ofthe probe card assembly of FIG. 4A, showing means for adjusting theorientation of the probe card insert of FIG. 4 relative to the probecard component, according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0056] This patent application is directed to probe card assemblies,components thereof, and methods of using same. As will be evident fromthe description that follows, the use of resilient (spring) contactstructures to effect pressure connections to terminals of an electroniccomponent is essential. The resilient contact structures are suitably(but not necessarily) implemented as “composite interconnectionelements”, such as have been described in the disclosure of theaforementioned U.S. patent application Ser. No. 08/452,255 (“PARENTCASE”), incorporated by reference herein.

[0057] According to an aspect of the invention, the probe elements(resilient contact structures extending from the top surface of thespace transformer component) are preferably formed as “compositeinterconnection elements” which are fabricated directly upon theterminals of the space transformer component of the probe card assembly.The “composite” (multilayer) interconnection element is fabricated bymounting an elongate element (“core”) to an electronic component,shaping the core to have a spring shape, and overcoating the core toenhance the physical (e.g., spring) characteristics of the resultingcomposite interconnection element and/or to securely anchor theresulting composite interconnection element to the electronic component.The resilient contact structures of the interposer component may also beformed as composite interconnection elements.

[0058] The use of the term “composite”, throughout the description setforth herein, is consistent with a ‘generic’ meaning of the term (e.g.,formed of two or more elements), and is not to be confused with anyusage of the term “composite” in other fields of endeavor, for example,as it may be applied to materials such as glass, carbon or other fiberssupported in a matrix of resin or the like.

[0059] As used herein, the term “spring shape” refers to virtually anyshape of an elongate element which will exhibit elastic (restorative)movement of an end (tip) of the elongate element with respect to a forceapplied to the tip. This includes elongate elements shaped to have oneor more bends, as well as substantially straight elongate elements.

[0060] As used herein, the terms “contact area”, “terminal”, “pad”, andthe like refer to any conductive area on any electronic component towhich an interconnection element is mounted or makes contact.

[0061] In an embodiment of the invention, the probe elements arecomposite interconnection elements comprising a core of a “soft”material having a relatively low yield strength which is overcoated witha “hard” material having a relativel high yield strength. For example, asoft material such as a gold wire is attached (e.g., by wire bonding) toa bond pad of a semiconductor device and is overcoated (e.g., byelectrochemical plating) with a hard material such nickel and itsalloys.

[0062] Vis-a-vis overcoating the core, single and multi-layerovercoatings, “rough” overcoatings having microprotrusions (see alsoFIGS. 5C and 5D of the PARENT CASE), and overcoatings extending theentire length of or only a portion of the length of the core, aredescribed. In the latter case, the tip of the core may suitably beexposed for making contact to an electronic component (see also FIG. 5Bof the PARENT CASE).

[0063] Generally, throughout the description set forth herein, the term“plating” is used as exemplary of a number of techniques for overcoatingthe core. It is within the scope of this invention that the core can beovercoated by any suitable technique including, but not limited to:various processes involving deposition of materials out of aqueoussolutions; electrolytic plating; electroless plating; chemical vapordeposition (CVD); physical vapor deposition (PVD); processes causing thedeposition of materials through induced disintegration of liquid orsolid precursors; and the like, all of these techniques for depositingmaterials being generally well known.

[0064] Generally, for overcoating the core with a metallic material suchas nickel, electrochemical processes are preferred, especiallyelectrolytic plating.

[0065] In another embodiment of the invention, the core is an elongateelement of a “hard” material, inherently suitable to functioning as aspring element, and is mounted at one end to a terminal of an electroniccomponent. The core, and at least an adjacent area of the terminal, ispreferably overcoated with a material which will enhance anchoring thecore to the terminal. In this manner, it is not necessary that the corebe well-mounted to the terminal prior to overcoating, and processeswhich are less potentially damaging to the electronic component may beemployed to “tack” the core in place for subsequent overcoating. These“friendly” processes include soldering, gluing, and piercing an end ofthe hard core into a soft portion of the terminal.

[0066] Preferably, the core is in the form of a wire. Alternatively, thecore is in the form of a ribbon.

[0067] Representative materials, both for the core and for theovercoatings, are disclosed.

[0068] In the main hereinafter, techniques involving beginning with arelatively soft (low yield strength) core, which is generally of verysmall dimension (e.g., 3.0 mil or less) are described. Soft materials,such as gold, which attach easily to semiconductor devices, generallylack sufficient resiliency to function as springs. (Such soft, metallicmaterials exhibit primarily plastic, rather than elastic deformation.)Other soft materials which may attach easily to semiconductor devicesand possess appropriate resiliency are often electrically nonconductive,as in the case of most elastomeric materials. In either case, desiredstructural and electrical characteristics can be imparted to theresulting composite interconnection element by the overcoating appliedover the core. The resulting composite interconnection element can bemade very small, yet can exhibit appropriate contact forces. Moreover, aplurality of such composite interconnection elements can be arranged ata fine pitch (e.g., 10 mils), even though they have a length (e.g., 100mils) which is much greater than the distance to a neighboring compositeinterconnection element (the distance between neighboringinterconnection elements being termed “pitch”).

[0069] It is within the scope of this invention that compositeinterconnection elements can be fabricated on a microminiature scale,for example as small springs for connectors and sockets, havingcross-sectional dimensions on the order of twenty-five microns (

m), or less. This ability to manufacture reliable interconnection havingdimensions measured in microns, rather than mils, squarely addresses theevolving needs of existing interconnection technology and future areaarray technology.

[0070] The composite interconnection elements of the present inventionexhibit superior electrical characteristics, including electricalconductivity, solderability and low contact resistance. In many cases,deflection of the interconnection element in response to applied contactforces results in a “wiping” contact, which helps ensure that a reliablecontact is made.

[0071] An additional advantage of the present invention is thatconnections made with the interconnection elements of the presentinvention are readily demountable. Soldering, to effect theinterconnection to a terminal of an electronic component is optional,but is generally not preferred at a system level.

[0072] According to an aspect of the invention, techniques are describedfor making interconnection elements having controlled impedance. Thesetechniques generally involve coating (e.g., electrophoretically) aconductive core or an entire composite interconnection element with adielectric material (insulating layer), and overcoating the dielectricmaterial with an outer layer of a conductive material. By grounding theouter conductive material layer, the resulting interconnection elementcan effectively be shielded, and its impedance can readily becontrolled. (See also FIG. 10K of the PARENT CASE.)

[0073] According to an aspect of the invention, interconnection elementscan be pre-fabricated as individual units, for later attachment toelectronic components. Various techniques for accomplishing thisobjective are set forth herein. Although not specifically covered inthis document, it is deemed to be relatively straightforward tofabricate a machine that will handle the mounting of a plurality ofindividual interconnection elements to a substrate or, alternatively,suspending a plurality of individual interconnection elements in anelastomer, or on a support substrate.

[0074] It should clearly be understood that the compositeinterconnection element of the present invention differs dramaticallyfrom interconnection elements of the prior art which have been coated toenhance their electrical conductivity characteristics or to enhancetheir resistance to corrosion.

[0075] The overcoating of the present invention is specifically intendedto substantially enhance anchoring of the interconnection element to aterminal of an electronic component and/or to impart desired resilientcharacteristics to the resulting composite interconnection element.Stresses (contact forces) are directed to portions of theinterconnection elements which are specifically intended to absorb thestresses.

[0076] It should also be appreciated that the present invention providesessentially a new technique for making spring structures. Generally, theoperative structure of the resulting spring is a product of plating,rather than of bending and shaping. This opens the door to using a widevariety of materials to establish the spring shape, and a variety of“friendly” processes for attaching the “falsework” of the core toelectronic components. The overcoating functions as a “superstructure”over the “falsework” of the core, both of which terms have their originsin the field of civil engineering.

[0077] A distinct advantage of the present invention is that probeelements (resilient contact structures) can be fabricated directly onterminals of a space transformer substrate component of a probe cardassembly without requiring additional materials, such as brazing orsoldering.

[0078] According to an aspect of the invention, any of the resilientcontact structures may be formed as at least two compositeinterconnection elements.

[0079] A Probe Card Assembly

[0080] The aforementioned U.S. patent application Ser. No. 08/554,902and its counterpart PCT/US95/14844 disclose a probe card assembly. FIG.1 of this patent application corresponds generally to FIG. 5 of thoseapplications.

[0081]FIG. 1 illustrates an embodiment of a probe card assembly 100which includes as its major functional components a probe card 102, aninterposer 104 and a space transformer 106, and which is suitable in usefor making temporary (pressure) electrical connections to asemiconductor wafer 108. In this exploded, cross-sectional view, certainelements of certain components are shown exaggerated, for illustrativeclarity. However, the vertical (as shown) alignment of the variouscomponents is properly indicated by the dashed lines in the figure. Itshould be noted that the interconnection elements (114, 116, 124,discussed in greater detail hereinbelow) are shown in full, rather thanin section.

[0082] The probe card component 102 is generally a conventional circuitboard substrate having a plurality (two of many shown) of contact areas(terminals) 110 disposed on the top (as viewed) surface thereof.Additional components (not shown) may be mounted to the probe card, suchas active and passive electronic components, connectors, and the like.The terminals 110 on the circuit board may typically be arranged at a100 mil pitch. The probe card 102 is suitably round, having a diameteron the order of 12 inches.

[0083] The interposer 104 includes a circuitized substrate 112. In themanner described hereinabove, a plurality (two of many shown) ofresilient (spring) interconnection elements 114 are mounted (by theirproximal ends) to and extend downward (as viewed) from the bottom (asviewed) surface of the substrate 112, and a corresponding plurality (twoof many shown) of resilient interconnection elements 116 are mounted (bytheir proximal ends) to and extend upward (as viewed) from the top (asviewed) surface of the substrate 112. The spring elements 114 areinterconnected (not shown) to the spring elements 116 in a conventionalmanner through the substrate 112.

[0084] Any of the spring shapes disclosed in any of the aforementionedcommonly-owned patents and patent applications are suitable for use asthe resilient interconnection elements 114 and 116, and they may beimplemented as “composite interconnection elements”. As a generalproposition, the tips (distal ends) of both the lower plurality 114 andof the upper plurality 116 of interconnection elements 114 and 116 areat a pitch which matches that of the terminals 110 of the probe cardcomponent 102, for example 100 mils.

[0085] The interconnection elements 114 and 116 are illustrated withexaggerated scale, for illustrative clarity. Typically, theinterconnection elements 114 and 116 would extend to an overall heightof 20-100 mils from respective bottom and top surfaces of the interposersubstrate 112. Generally, the height of the interconnection elements isdictated by the amount of compliance desired.

[0086] The space transformer component 106 includes a suitablecircuitized substrate 118 such as a multi-layer ceramic substrate havinga plurality (two of many shown) of terminals (contact areas, pads) 120disposed on the lower (as viewed) surface thereof and a plurality (twoof many shown) of terminals (contact areas, pads) 122 disposed on theupper (as viewed) surface thereof. In this example, the lower pluralityof contact pads 120 is disposed at the pitch of the tips of theinterconnection elements 116 (e.g., 100 mils), and the upper pluralityof contact pads 122 is disposed at a finer (closer) pitch (e.g., 50mils).

[0087] A plurality (two of many shown) of resilient (spring)interconnection elements 124 (also referred to as “probes” or “probeelements”) are mounted (by their proximal ends) to the terminals 122 andextend upward (as viewed) from the top (as viewed) surface of the spacetransformer substrate 118. As illustrated, these probe elements 124 aresuitably arranged so that their tips (distal ends) are spaced at an evenfiner pitch (e.g., 10 mils) than their proximal ends, thereby augmentingthe pitch reduction of the space transformer 106. These resilientcontact structures (interconnection elements) 124 are preferably, butnot necessarily, the aforementioned “composite interconnectionelements”.

[0088] It is within the scope of the invention that the probe elements(124) can be fabricated on a sacrificial substrate and subsequentlymounted to the terminals (122) of the space transformer component (106),in the manner discussed in the aforementioned commonly-owned U.S. patentapplication Ser. No. 08/788,740 and its counterpart PCT/US96/08107.

[0089] As is known, a semiconductor wafer 108 includes a plurality ofdie sites (not shown) formed by photolithography, deposition, diffusion,and the like, on its front (lower, as viewed) surface. Typically, thesedie sites are fabricated to be identical to one another. However, as isknown, flaws in either the wafer itself or in any of the processes towhich the wafer is subjected to form the die sites, can result incertain die sites being non-functional, according to well establishedtest criteria. Often, due to the difficulties attendant probing diesites prior to singulating semiconductor dies from a semiconductorwafer, testing is performed after singulating and packaging thesemiconductor dies. When a flaw is discovered after packaging thesemiconductor die, the net loss is exacerbated by the costs attendant topackaging the die. Semiconductor wafers typically have a diameter of atleast 6 inches, including at least 8 inches.

[0090] Each die site typically has a number of contact areas (e.g., bondpads), which may be disposed at any location and in any pattern on thesurface of the die site. Two (of many) bond pads 126 of a one of the diesites are illustrated in the figure.

[0091] A limited number of techniques are known for testing the diesites, prior to singulating the die sites into individual semiconductordies. A representative prior art technique involves fabricating a probecard insert having a plurality of tungsten “needles” embedded in andextending from a ceramic substrate, each needle making a temporaryconnection to a given one of the bond pads. Such probe card inserts areexpensive and somewhat complex to manufacture, resulting in theirrelatively high cost and in a significant lead time to obtain. Given thewide variety of bond pad arrangements that are possible in semiconductordies, each unique arrangement requires a distinct probe card insert.

[0092] The rapidity with which unique semiconductor dies aremanufactured highlights the urgent need for probe card inserts that aresimple and inexpensive to manufacture, with a short turnaround time. Theuse of a space transformer (106) having resilient (spring) contactelements (124) mounted thereto and extending therefrom as a probe cardinsert addresses this need.

[0093] In use, the interposer 104 is disposed on the top (as viewed)surface of the probe card 102, and the space transformer 106 is stackedatop (as viewed) the interposer 104 so that the interconnection elements114 make a reliable pressure contact with the contact terminals 110 ofthe probe card 102, and so that the interconnection elements 116 make areliable pressure contact with the contact pads 120 of the spacetransformer 106. Any suitable mechanism for stacking these componentsand for ensuring such reliable pressure contacts may be employed, asuitable one of which is described hereinbelow.

[0094] The probe card assembly 100 includes the following majorcomponents for stacking the interposer 106 and the space transformer 106onto the probe card 102:

[0095] a rear mounting plate 130 made of a rigid material such asstainless steel,

[0096] an actuator mounting plate 132 made of a rigid material such asstainless steel,

[0097] a front mounting plate 134 made of a rigid material such asstainless steel,

[0098] a plurality (two of many shown, three is preferred) ofdifferential screws including an outer differential screw element 136and an inner differential screw element 138,

[0099] a mounting ring 140 which is preferably made of a springymaterial such as phosphor bronze and which has a pattern of springy tabs(not shown) extending therefrom,

[0100] a plurality (two of many shown) of screws 142 for holding themounting ring 138 to the front mounting plate 134 with the spacetransformer 106 captured therebetween,

[0101] optionally, a spacer ring 144 disposed between the mounting ring140 and the space transformer 106 to accommodate manufacturingtolerances, and

[0102] a plurality (two of many shown) of pivot spheres 146 disposedatop (as viewed) the differential screws (e.g., atop the innerdifferential screw element 138).

[0103] The rear mounting plate 130 is a metal plate or ring (shown as aring) disposed on the bottom (as shown) surface of the probe card 102. Aplurality (one of many shown) of holes 148 extend through the rearmounting plate.

[0104] The actuator mounting plate 132 is a metal plate or ring (shownas a ring) disposed on the bottom (as shown) surface of the rearmounting plate 130. A plurality (one of many shown) of holes 110 extendthrough the actuator mounting plate. In use, the actuator mounting plate132 is affixed to the rear mounting plate 130 in any suitable manner,such as with screws (omitted from the figure for illustrative clarity).

[0105] The front mounting plate 134 is a rigid, preferably metal ring.In use, the front mounting plate 134 is affixed to the rear mountingplate 130 in any suitable manner, such as with screws (omitted from thefigure for illustrative clarity) extending through corresponding holes(omitted from the figure for illustrative clarity) through the probecard 102, thereby capturing the probe card 102 securely between thefront mounting plate 134 and rear mounting plate 130.

[0106] The front mounting plate 134 has a flat bottom (as viewed)surface disposed against the top (as viewed) surface of the probe card102. The front mounting plate 134 has a large central openingtherethrough, defined by an inner edge 112 the thereof, which is sizedto permit the plurality of contact terminals 110 of the probe card 102to reside within the central opening of the front mounting plate 134, asshown.

[0107] As mentioned, the front mounting plate 134 is a ring-likestructure having a flat bottom (as viewed) surface. The top (as viewed)surface of the front mounting plate 134 is stepped, the front mountingplate being thicker (vertical extent, as viewed) in an outer regionthereof than in an inner region thereof. The step, or shoulder islocated at the position of the dashed line (labelled 114), and is sizedto permit the space transformer 106 to clear the outer region of thefront mounting plate and rest upon the inner region of the frontmounting plate 134 (although, as will be seen, the space transformeractually rests upon the pivot spheres 146).

[0108] A plurality (one of many shown) of holes 114 extend into theouter region of the front mounting plate 134 from the top (as viewed)surface thereof at least partially through the front mounting plate 134(these holes are shown extending only partially through the frontmounting plate 134 in the figure) which, as will be seen, receive theends of a corresponding plurality of the screws 142. To this end, theholes 114 are threaded holes. This permits the space transformer 106 tobe secured to the front mounting plate by the mounting ring 140, henceurged against the probe card 102.

[0109] A plurality (one of many shown) of holes 118 extend completelythrough the thinner, inner region of the front mounting plate 134, andare aligned with a plurality (one of many shown) of corresponding holes160 extending through the probe card 102 which, in turn, are alignedwith the holes 148 in the rear mounting plate and the holes 110 in theactuator mounting plate 138.

[0110] The pivot spheres 146 are loosely disposed within the alignedholes 118 and 160, at the top (as viewed) end of the inner differentialscrew elements 138. The outer differential screw elements 136 threadinto the (threaded) holes 110 of the actuator mounting plate 132, andthe inner differential screw elements 138 thread into a threaded bore ofthe outer differential screw elements 136. In this manner, very fineadjustments can be made in the positions of the individual pivot spheres146. For example, the outer differential screw elements 136 have anexternal thread of 72 threads-per-inch, and the inner differential screwelements 138 have an external thread of 80 threads-per inch. Byadvancing an outer differential screw element 136 one turn into theactuator mounting plate 132 and by holding the corresponding innerdifferential screw element 138 stationary (with respect to the actuatormounting plate 132), the net change in the position of the correspondingpivot sphere 146 will be ‘plus’ {fraction (1/72)} (0.0139) ‘minus’{fraction (1/80)} (0.0125) inches, or 0.0014 inches. This permits facileand precise adjustment of the planarity of the space transformer 106vis-a-vis the probe card 102. Hence, the positions of the tips (topends, as viewed) of the probes (interconnection elements) 124 can bechanged, without changing the orientation of the probe card 102. Theimportance of this feature, a technique for performing alignment of thetips of the probes, and alternate mechanisms (means) for adjusting theplanarity of the space transformer are discussed in greater detailhereinbelow. Evidently, the interposer 104 ensures that electricalconnections are maintained between the space transformer 106 and theprobe card 102 throughout the space transformer's range of adjustment,by virtue of the resilient or compliant contact structures disposed onthe two surfaces of the interposer.

[0111] The probe card assembly 100 is simply assembled by placing theinterposer 104 within the opening 112 of the front mounting plate 134 sothat the tips of the interconnection elements 114 contact-the contactterminals 110 of the probe card 102, placing the space transformer 106on top of the interposer 104 so that the tips of the interconnectionelements 116 contact the contact pads 120 of the space transformer 106,optionally placing a spacer 144 atop the space transformer 106, placingthe mounting ring 140 over the spacer 144, and inserting the screws 142through the mounting ring 140 through the spacer 144 and into the holes114 of the front mounting plate 134, and mounting this “subassembly” tothe probe card 102 by inserting screws (one shown partially as 155)through the rear mounting plate 130 and through the probe card 102 intothreaded holes (not shown) in the bottom (as viewed) surface of thefront mounting plate 134. The actuator mounting plate 138 can then beassembled (e.g., with screws, on of which is shown partially as 156) tothe rear mounting plate 130, pivot spheres 160 dropped into the holes150 of the actuator mounting plate 132, and the differential screwelements 136 and 138 inserted into the holes 150 of the actuatormounting plate 132.

[0112] In this manner, a probe card assembly is provided having aplurality of resilient contact structures (124) extending therefrom formaking contact with a plurality of bond pads (contact areas) onsemiconductor dies, prior to their singulation from a semiconductorwafer, at a fine pitch which is commensurate with today's bond padspacing. Generally, in use, the assembly 100 would be employed upsidedown from what is shown in the figure, with the semiconductor waferbeing pushed (by external mechanisms, not shown) up onto the tips of theresilient contact structures (124).

[0113] As is evident from the figure, the front mounting plate(baseplate) 134 determines the position of the interposer 104 vis-a-visthe probe card 102. To ensure accurate positioning of the front mountingplate 134 vis-a-vis the probe card 102, a plurality of alignmentfeatures (omitted from the figure for illustrative clarity) such as pinsextending from the front mounting plate) and holes extending into theprobe card 102 may be provided.

[0114] It is within the scope of this invention that any suitableresilient contact structures (114, 116, 124) be employed on theinterposer (104) and/or the space transformer (106), including tabs(ribbons) of phosphor bronze material or the like brazed or soldered tocontact areas on the respective interposer or space transformer.

[0115] It is within the scope of this invention that the interposer(104) and the space transformer (106) can be pre-assembled with oneanother, such as with spring clips which are described as element, 486of FIG. 29 of the aforementioned copending, commonly-ownedPCT/US94/13373, extending from the interposer substrate.

[0116] It is within the scope of this invention that the interposer(104) be omitted, and in its stead, a plurality of resilient contactstructures comparable to 114 be mounted directly to the contact pads(120) on the lower surface of the space transformer. However, achievingcoplanarity between the probe card and the space transformer would bedifficult. A principal function of the interposer is to providecompliance to ensure such coplanarity.

[0117] As illustrated in FIGS. 5A and 5B of the aforementioned U.S.patent application Ser. No. 08/554,902 and its counterpartPCT/US95/14844, the top (as viewed in FIG. 5 therein, or in FIG. 1herein) can be provided with a plurality of terminals to which springcontact elements are mounted in a pattern that corresponds a singlesemiconductor die or to a plurality (e.g., four or more) semiconductordies which are resident on a semiconductor wafer.

[0118] Aligning the Probe Card Assembly

[0119] The aforementioned U.S. patent application Ser. No. 08/554,902and its counterpart PCT/US95/14844 disclose a technique for aligningthee probe card assembly. FIG. 2 of this patent application correspondsgenerally to FIG. 7 of those applications.

[0120]FIG. 2 illustrates a technique 200 of aligning a probe cardassembly such as the probe card assembly 100 of FIG. 1. The view of FIG.2 is partially assembled, with the major components in contact with oneanother.

[0121] A problem addressed head on by this invention is that it is oftendifficult to align the contact tips of a probe card (or probe cardinsert) with respect to a semiconductor wafer being tested. It isessential that tolerances on the coplanarity of the tips of the probesand the surface of the wafer be held to a minimum, to ensure uniformreliable contact pressure at each the tip 124 a (top ends, as viewed) ofeach probe (i.e, the resilient contact structures 124). As discussedhereinabove, a mechanism (e.g., differential screws 136 and 138) isprovided in the probe card assembly for adjusting the planarity of thetips 124 a of the probes by acting upon the space transformer 106. Inthis figure, the space transformer substrate 106 is illustrated withinternal connection between the top terminals and the bottom terminalsthereof.

[0122] Prior to employing the probe card assembly to perform testing ona semiconductor wafer, the alignment of the probe tips is measured and,if necessary, adjusted to ensure that the probe tips 124 a will becoplanar with semiconductor wafers that are subsequently presented tothe probe card assembly (i.e., urged against the probe tips).

[0123] Generally, a wafer tester (not shown) in which the probe cardassembly is mounted, will have a mechanism (not shown) for conveyingsemiconductor wafers into the region of the probe card assembly andurging the semiconductor wafers against the probe tips 124 a. To thisend, semiconductor wafers are held by a chuck mechanism (not shown). Forpurposes of this discussion, it is assumed that the tester and chuckmechanism are capable of moving wafer-after-wafer into a precise,repeatable location and orientation—the precise location of the waferfunctioning as a “reference plane”.

[0124] According to the invention, in order to align the tips 524 avis-a-vis the expected orientation of a semiconductor wafer, in otherwords vis-a-vis the reference plane, a flat electrically-conductivemetal plate 202 is mounted in the tester in lieu of a semiconductorwafer. The flat metal plate 202 functions as an “ersatz” or “virtual”wafer, for purposes of aligning the tips 124 a of the probe elements124.

[0125] Each probe element 124 is associated with a one of a plurality ofterminals (not shown) on the probe card 102, a conductive paththerebetween being constituted by a selected one of the probe elements124, an associated selected one of the resilient contact structures 116and an associated selected one of the resilient contact structures 114,and wiring layers (not shown) within the probe card 102. The probe cardterminals may be in the form of surface terminals, terminals of asocket, or the like. A cable 204 connects between the probe card 102 anda computer (tester) 206 which has a display monitor 208. The presentinvention is not limited to using a computing device, nor to a displaymonitor.

[0126] In this example, it is assumed that one hundred pressure contactsare sought to be effected between one hundred probe tips 124 a arrangedin a 10×10 rectangular array and one hundred terminals (e.g., bond pads)of a semiconductor wafer. The present invention is not, however, limitedto any particular number of probe tips or any particular layout of bondpads.

[0127] The flat metal plate 202 is carried by the chuck (not shown) andurged (advanced, as indicated by the arrow labelled “A”) against theprobe tips 124 a. This is done in a relatively gradual manner, so thatit can be ascertained whether the probe tips 124 a all contact the flatmetal plate in unison (not likely), or whether certain ones of the probetips 124 a are contacted by the flat metal plate 202 prior to remainingones of the probe tips 124 a. In the illustration, the seventy-onefilled circles (dots) within the area 210 on the monitor 208 indicatethat seventy-one of the probe tips 124 a have been contacted by the flatmetal plate 202 prior to the remaining twenty-nine of the probe tips 124a (illustrated as empty circles) having been contacted by the flat metalplate 202. Based on this visual representation, it is evident that thespace transformer 106 (or, possibly, the metal plate 202) is tilted(canted) to the left (as viewed) downwards (out of the page, as viewed),and the orientation of the space transformer 506 can readily be adjustedby suitable adjustments of the differential screws 136 and 138.

[0128] The adjustments necessary to achieve the desired goal of planar,simultaneous contact of all of the tips 124 a with the flat metal plate202, without altering the orientation of the probe card 1502, so thatall of the probe tips 124 a make substantially simultaneous contact withthe flat metal plate 202 are readily calculated, either on-line oroff-line. By making the calculated adjustments, the tips 124 a of theprobes 124 will subsequently make substantially simultaneous contactwith bond pads on semiconductor wafers being tested.

[0129] The “go/no-go” (contact/no contact) type of testing discussed inthe previous paragraph is illustrative of a first “order” of alignmentthat is facilitated by the probe card assembly of the present invention.A second “order” of alignment is readily performed by recording (e.g.,in the computer memory) the sequence (order) in which the probe elementtips contact the metal plate. The first tip to contact the metal plategenerally will generally represent a corner of the space transformerthat is too “high”, and needs to be lowered (e.g., by adjusting thedifferential screws). Likewise, the last tip to contact the metal platewill generally represent a corner of the space transformer that is too“low”, and needs to be heightened (e.g., by adjusting the differentialscrews). It is within the scope of this invention that any suitablealgorithm can be employed to determine the adjustments required to bemade, based on the sequence of tips contacting the metal plate. It isalso within the scope of this invention that a resistance (e.g., toground) between each probe tip 124 a and the flat metal plate 202 can bemeasured and displayed as a numeral, or symbol, or dot color, or thelike, indicative of the measured resistance, rather than merely as afilled circle versus an unfilled circle on the display monitor, althoughsuch is generally not preferred.

[0130] It is within the scope of this invention that any suitablemechanism can be employed for adjusting the orientation of the spacetransformer 106—in other words, planarizing the tips 124 a of probeelements 124. Alternatives to using the differential screws (136, 138)arrangement discussed hereinabove would be to use servo mechanisms,piezoelectric drivers or actuators, magnetostrictive devices,combinations thereof (e.g., for gross and fine adjustments), or the liketo accomplish such planarizing.

[0131] Feedback and Automatic Planarizing

[0132] The aforementioned U.S. patent application Ser. No. 08/554,902and its counterpart PCT/US95/14844 disclose an alternate (i.e., to thedifferential screws etc.) mechanism for aligning the probe cardassembly. FIG. 3 of this patent application corresponds generally toFIG. 7A of those applications.

[0133]FIG. 3 illustrates an automated technique 300 for adjusting thespatial orientation of the space transformer (not shown in this view).In this example, an actuator mechanism 302 (labelled “ACT”) issubstituted for the differential screws (136, 138) and operates inresponse to signals from the computer (e.g., 206). Three such mechanisms302 can be substituted for the three pairs of differential screwelements in a straightforward manner. Similar elements in FIG. 3 arelabelled with identical numbers as appear in FIG. 2, and severalelements appearing in FIG. 2 are omitted from the view of FIG. 3, forillustrative clarity.

[0134] It is also within the scope of this invention that the mechanism(particularly an automated mechanism as illustrated in FIG. 3) forplanarizing the space transformer (106) can be disposed other than asshown in the exemplary embodiments described herein. For example, asuitable mechanism could be located between the top (as viewed) surfaceof the probe card (102) and the front mounting plate (134), orincorporated into the front mounting plate (134). The key feature ofusing any of these mechanisms is the ability to alter the angle(orientation) of the space transformer (e.g., 106) without requiring theorientation of the probe card (102) to be altered.

[0135] As used herein, the term “resilient”, as applied to contactstructures, implies contact structures (interconnection elements) thatexhibit primarily elastic behavior in response to an applied load(contact force), and the term “compliant” implies contact structures(interconnection elements) that exhibit both elastic and plasticbehavior in response to an applied load (contact force). As used herein,a “compliant” contact structure is a “resilient” contact structure. Thecomposite interconnection elements of the present invention are aspecial case of either compliant or resilient contact structures.

[0136] It is within the scope of the invention, and is generallypreferred, that although the interconnection elements 514 and 516 areillustrated in FIG. 5 as single interconnection elements, eachillustrated element is readily implemented as an interconnectionstructure having two or more interconnection elements in the mannerdescribed hereinabove with respect to FIG. 3A, to ensure that reliablepressure contacts are made to the respective contact terminals 510 ofthe probe card 502 and contact pads 520 of the space transformer 506.

[0137] Mounting the Probe Elements to Silicon

[0138] As mentioned hereinabove, the use of a space transformercomponent (106) in the probe card assembly (100) raises some challenges.For example, when making connections to semiconductor devices to operatethem (i.e., burn-in and/or test), the devices will generate heat andexpand according to a given coefficient of thermal expansion. Thus,although it is desirable to have a space transformer component that hasa coefficient of thermal expansion closely matching that of the silicondevice(s), it would be preferable to have the probe elements (124)mounted to and extending from a substrate that has a coefficient ofthermal expansion which exactly matches that of the silicon devicesbeing operated.

[0139] According to the invention, the probe elements (124) are mountedto and extend from a silicon substrate having a coefficient of thermalexpansion which substantially exactly matches that of a wafer (108)being contacted.

[0140] Thus, it is within the scope of this invention that the spacetransformer itself (106) is fabricated from a silicon wafer andprovided, if need be, with a rigid backing substrate (not shown). Also,as it turns out, it is easier and more reliable to mount certain typesof free-standing elongate interconnectin elements to a silicon substratethan to a ceramic substrate such as a conventional space transformer.For example, the “composite interconnection elements” discussedhereinbove.

[0141] It is, however, preferred to take advantage of a siliconsubstrate carrying the probe elements to make beneficial modificationsto the overall probe card assembly.

[0142]FIGS. 4 and 4A illustrate a probe card insert 400 and probe cardassembly 450 employing the probe card insert 400, respectively.Generally, instead of using a space transformer (106), in thisembodiment the resilient (spring) interconnection (probe) elements 424(compare 124) are mounted to and extend from a first plurality (four ofmany shown in FIG. 4, two of the four shown in FIG. 4A) of terminals 422(compare 122) of an interconnection substrate 418 (compare 118) whichsuch as a piece of or an entire silicon wafer. Also, instead of makingelectrical connections from the probe card 402 (compare 102) to theprobe elements 424 via the intermediary of an interposer (104),electrical connections are made from the probe card 402 to the probeelements 424 via a flexible ribbon-like conductor 404.

[0143] The flexible ribbon-like cable 404 has two ends 404 a and 404 b.The first end 404 a is connected to a second plurality (two of manyshown in FIG. 4, one of the two shown in FIG. 4A) of terminals 423disposed on the interconnection substrate 418. The second end 404 b isconnected to the probe card 402, suitably by a plug 416 at the end 402 bof the cable 404 which mates with a corresponding socket 414 which ismounted to the probe card 402 (or vice-versa).

[0144] One having ordinary skill in the art to which this invention mostnearly pertains will recognize that, although not shown, each of theterminals 423 are readily interconnected via (e.g., within) thesubstrate 418 with corresponding ones of the terminals 422.

[0145] As best viewed in FIG. 4, there are a plurality (two of manyshown) of conductive lines (fingers) 405 extending from the first end404 a of the cable 404. These 405 are suitably ribbon-like conductorsand, in the manner of tape automated bonding (TAB) are readily bonded tothe respective terminals 423. Also, the cable 404 is readily made tohave controlled impedance, being provided with additional conductors(not shown) which are connected to ground.

[0146] As illustrated schematically by the pair of two-headed arrows inFIG. 4A, there is preferably provided means for controlling theorientation (e.g., planarity) of the interconnection substrate 418 withrespect to the probe card 402. This means is suitably similar to themeans for controlling orientation described hereinabove with respect toFIG. 1. Taking into account the inherent fragilility of a siliconsubstrate 418, there is preferably provided a rigid backing (support)member 406 for the silicon substrate 418. The support member 406 issuitably a plate of metal, such as brass or steel, and is sufficientlystrong (e.g., stiff and thick) to prevent the silicon substrate 418 fromflexing when the probe card assembly is urged against a WUT (not shown).

[0147] As mentioned above, the interconnection substrate 418 ispreferably silicon, to exactly match the coefficient of thermalexpansion of the WUT (not shown, see 108 in FIG. 1).

[0148] When silicon is used for the interconnection substrate 418, it isreadily provided with active devices, such as field effect transistors(FETs), using conventional semiconductor processing techniques. In thismanner, for example, when simultaneously (i.e., in one touchdown)probing a plurality of memory devices on a WUT and it is determined thata one of the plurality has a failed (e.g., is shorted out), the “bad”device under test (DUT) can be shut down.

[0149] Silicon (418) offers additional advantages over ceramic (418) forthe substrate to which the probe elements (124, 424) are mounted. Itgenerally has lower series resistance. And it offers more routing (e.g.,from the terminals 423 to the terminals 422) flexibility.

[0150] As described hereinabove, the electrical function of theinterposer (104) has been “replaced” by the cable 404. However, it willbe recalled that the interposer (104) also worked in concert with themeans for orienting the probe card insert, mechanically biasing thesubstrate of the probe card insert away from the probe card. Thismechanical function, shown by the pair of two-headed arrows in FIG. 4A,can be replaced with any suitable means, such as coil springs.

[0151]FIG. 4B shows an example of a complete probe card assembly 480assembled in the manner described hereinabove, utilizing differentialscrews (compare FIG. 1) and three (two visible) simple coil springs 482between the top (as viewed) surface of the probe card 402 and the bottom(as viewed) surface of the support member 406. As is evident from thisfigure, the support member 406 can have the same general shape and sizeas the previously-mentioned space transformer 106, in which case severalother elements (i.e., those numbered 1xx) of the previous embodiment 100can be employed in like manner in the embodiment 480.

[0152] Although the invention has been illustrated and described indetail in the drawings and foregoing description, the same is to beconsidered as illustrative and not restrictive in character—it beingunderstood that only preferred embodiments have been shown anddescribed, and that all changes and modifications that come within thespirit of the invention are desired to be protected. Undoubtedly, manyother “variations” on the “themes” set forth hereinabove will occur toone having ordinary skill in the art to which the present invention mostnearly pertains, and such variations are intended to be within the scopeof the invention, as disclosed herein. Several of these variations areset forth in the parent case.

[0153] For example, prefabricated contact tip structures are readilyjoined to the the free ends of the probe elements (424) in the mannerdescribed with respect to FIGS. 8A-8E of the aforementioned U.S. patentapplication Ser. No. 08/554,902 and its counterpart PCT/US95/14844.

[0154] For example, it has been suggested hereinabove that the compositeinterconnection elements of the present invention are but an example ofsuitable resilient contact structures that can be mounted directly toterminals of a space transformer component of a probe card assembly. Forexample, it is within the scope of this invention that needles of aninherently resilient (relatively high yield strength) material, such astungsten, can be coated with a material, such as solder or gold, to makethem solderable, optionally supported in a desired pattern, and joinedsuch as by soldering to the terminals (424) of the interconnectionsubstrate (418).

What is claimed is:
 1. Probe card insert for a probe card assembly,comprising: a silicon substrate having a first plurality of terminals; aplurality of probe elements mounted to the first plurality of terminalsa plurality of connections between selected ones of the first pluralityof terminals to selected ones of a plurality of probe card contacts, andresilient support means for positioning the silicon substrate away fromand generally parallel to a probe card.
 2. Probe card insert, accordingto claim 1, further comprising: pre-fabricated contact tip structuresmounted to ends of the plurality of probe elements.
 3. Probe cardinsert, according to claim 1, wherein: the probe elements are compositeinterconnection elements.
 4. Probe card insert, according to claim 1,further comprising: means for providing electrical connections, via thesilicon substrate, to the probe elements.
 5. Probe card insert,according to claim 4, wherein: the means for providing electricalconnections is a second plurality of terminals on the silicon substrate;and said second plurality of terminals are connected within the siliconsubstrate to the first plurality-of terminals.